One of the difficulties encountered when displaying motion video from a standard (e.g. NTSC) video source on a high-resolution graphics screen is that of synchronizing the two independent "rasters". There is no inherent relationship between the timing (synchronization) of the two independent sources. If one were to try to use a conventional memory architecture, it would be extremely difficult to synchronize the write operation, which is synchronous with the incoming video, with the read operation, which must be synchronous with the high-resolution display on which the video is ultimately presented.
Another challenge is presented by the high speed with which the video information must be manipulated in order to achieve full-motion video performance. Attempting to do this with a conventional display controller design risks having inadequate performance.
Yet another challenge is presented by the fact that the manner in which television signals are displayed is fundamentally different from the method used by most high-resolution displays. The inherently interlaced characteristic of the incoming video in TV information must be eliminated in order to present it on the non-interlaced high-resolution graphics screen. Several possibilities exist for solving this problem, each having relative advantages and disadvantages.